Edmund Kelleher

Academic website

Publications

Journal papers

09 10 11 12 13 14 15 2016

  1. Towards 'smart lasers': self-optimisation of an ultrafast pulse source using a genetic algorithm

    R. I. Woodward and E. J. R. Kelleher

    arXiv:1607.05688 [physics.optics] (2016) or Download PDF [Show abstract]

    Short-pulse fibre lasers are a complex dynamical system possessing a broad space of operating states that can be accessed through control of cavity parameters. Determination of target regimes is a multi-parameter global optimisation problem. Here, we report the implementation of a genetic algorithm to intelligently locate optimum parameters for stable single-pulse mode-locking in a Figure-8 fibre laser, and fully automate the system turn-on procedure. Stable ultrashort pulses are repeatably achieved by employing a compound fitness function that monitors both temporal and spectral output properties of the laser. Our method of encoding photonics expertise into an algorithm and applying machine-learning principles paves the way to self-optimising `smart' optical technologies. [Hide abstract]

  2. Characterization of the second-and third-order nonlinear optical susceptibilities of monolayer MoS2 using multiphoton microscopy

    R.I. Woodward, R.T. Murray, C.F. Phelan, R.E.P. de Oliveira, T.H. Runcorn, E.J.R. Kelleher, S Li, E.C. de Oliveira, G.J.M. Fechine, G. Eda, C.J.S. de Matos

    arXiv:1606.08093 [cond-mat.mes-hall] (2016) or Download PDF [Show abstract]

    We report second- and third-harmonic generation in monolayer MoS2 as a tool for imaging and accurately characterizing the material's nonlinear optical properties under 1560 nm excitation. Using a surface nonlinear optics treatment, we derive expressions relating experimental measurements to second- and third-order nonlinear sheet susceptibility magnitudes, obtaining values of |χs(2)|=2x10-20 m2 V-1 and for the first time for monolayer MoS2, |χs(3)|=2x10-28 m3 V-2. Experimental comparisons between MoS2 and graphene are also performed, demonstrating ~4 times stronger third-order nonlinearity in monolayer MoS2, highlighting the material's potential for nonlinear photonics in the telecommunications C band. [Hide abstract]

  3. Theory of edge-state optical absorption in two-dimensional transition metal dichalcogenide flakes

    Maxim Trushin, Edmund J. R. Kelleher and Tawfique Hasan

    arXiv:1602.06298 [cond-mat.mes-hall] (2016) or Download PDF [Show abstract]

    We develop an analytical model to describe sub-bandgap optical absorption in two-dimensional semiconducting transition metal dichalcogenide (s-TMD) nanoflakes. The material system represents an array of few-layer molybdenum disulfide crystals, randomly orientated in a polymer matrix. We propose that optical absorption involves direct transitions between electronic edge-states and bulk-bands, depends strongly on the carrier population, and is saturable with sufficient fluence. For excitation energies above half the bandgap, the excess energy is absorbed by the edge-state electrons, elevating their effective temperature. Our analytical expressions for the linear and nonlinear absorption could prove useful tools in the design of practical photonic devices based on s-TMDs. [Hide abstract]

  4. Highly efficient mid-infrared difference-frequency generation using synchronously pulsed fiber lasers

    R. T. Murray, T. H. Runcorn, E. J. R. Kelleher and J. R. Taylor

    Optics Letters, Vol. 41, 2446 (2016) or Download PDF [Show abstract]

    We report the development of a high average power, picosecond-pulse, mid-infrared source based on difference-frequency generation (DFG) of two synchronous master oscillator power fiber amplifier systems. The generated idler can be tuned over the range 3.28–3.45 μm delivering greater than 3.4 W of average power, with a maximum pump to total DFG power conversion efficiency of 78%. The benefits of a synchronously pumped scheme, compared to CW seeding of DFG sources, are discussed. [Hide abstract]

  5. Dark solitons in laser radiation build-up dynamics

    R. I. Woodward and E. J. R. Kelleher

    Physical Review E, Vol. 93, 032221 (2016) or Download PDF [Show abstract]

    We reveal the existence of slowly decaying dark solitons in the radiation build-up dynamics of bright pulses in all-normal dispersion mode-locked fiber lasers, numerically modeled in the framework of a generalized nonlinear Schrodinger equation. The evolution of noise perturbations to quasistationary dark solitons is examined, and the significance of background shape and soliton-soliton collisions on the eventual soliton decay is established. We demonstrate the role of a restoring force in extending soliton interactions in conservative systems to include the effects of dissipation, as encountered in laser cavities, and generalize our observations to other nonlinear systems. [Hide abstract]

  6. Modulation Instability and Phase-Shifted Fermi-Pasta-Ulam Recurrence

    O. Kimmoun, H. C. Hsu, H. Branger, M. S. Li, Y. Y. Chen, C. Kharif, M. Onorato, E. J. R. Kelleher, B. Kibler, N. Akhmediev and A. Chabchoub

    Scientific Reports, Vol. 6, 28516 (2016) or Download PDF [Show abstract]

    Instabilities are common phenomena frequently observed in nature, sometimes leading to unexpected catastrophes and disasters in seemingly normal conditions. One prominent form of instability in a distributed system is its response to a harmonic modulation. Such instability has special names in various branches of physics and is generally known as modulation instability (MI). The MI leads to a growth-decay cycle of unstable waves and is therefore related to Fermi-Pasta-Ulam (FPU) recurrence since breather solutions of the nonlinear Schrödinger equation (NLSE) are known to accurately describe growth and decay of modulationally unstable waves in conservative systems. Here, we report theoretical, numerical and experimental evidence of the effect of dissipation on FPU cycles in a super wave tank, namely their shift in a determined order. In showing that ideal NLSE breather solutions can describe such dissipative nonlinear dynamics, our results may impact the interpretation of a wide range of new physics scenarios. [Hide abstract]

  7. Special Section Guest Editorial: 2-D Materials for Optics and Photonics

    Han Zhang, Edmund Kelleher, Juejun Hu

    Optical Engineering, Vol. 55, 081301 (2016) or Download PDF [Show abstract]

    Throughout the last decade, interest has grown significantly in the photonic applications of 2-D materials since the emergence of graphene. The unique optical and electronic properties of graphene, including broadband absorption, high electron mobility, and ultrafast carrier dynamics, qualify graphene as a next-generation platform for advanced optoelectronic devices. In addition to semimetallic graphene, topological insulators, semiconducting transition metal dichalcogenides, and insulating hexagonal boron nitride have emerged, offering similarly fascinating, yet distinct, optical properties. [Hide abstract]

  8. Surfactant-aided exfoliation of molydenum disulphide for ultrafast pulse generation through edge-state saturable absorption

    R. C. T. Howe, R. I. Woodward, G. Hu, Z. Yang, E. J. R. Kelleher and T. Hasan

    Phys. Stat. Solidi (b), Vol. 253, 911 (2016) or Download PDF [Show abstract]

    We use liquid phase exfoliation to produce dispersions of molybdenum disulphide (MoS2) nanoflakes in aqueous surfactant solutions. The chemical structures of the bile salt surfactants play a crucial role in the exfoliation and stabilization of MoS2. The resultant MoS2 dispersions are heavily enriched in single and few (<6) layer flakes with large edge to surface area ratio. We use the dispersions to fabricate free-standing polymer composite wide-band saturable absorbers to develop mode-locked and Q- switched fibre lasers, tunable from 1535-1565 and 1030-1070 nm, respectively. We attribute this sub-bandgap optical absorption and its nonlinear saturation behaviour to edge-mediated states introduced within the material band-gap of the exfoliated MoS2 nanoflakes. [Hide abstract]

  9. Stable gain-switched thulium fiber laser with 140 nm tuning range

    F. Wang, Y. Meng, E. J. R. Kelleher, G. Guo, Y. Li, Y. Xu and S. Zhu

    IEEE Photon. Technol. Lett., Vol. 28, 1340 (2016) or Download PDF [Show abstract]

    We demonstrate a gain-switched thulium fiber laser that can be continuously tuned over 140 nm, while maintaining stable nanosecond single-pulse operation. To the best of our knowledge, this system represents the broadest tuning range for a gain-switched fiber laser. The system simplicity and wideband wavelength tunability combined with the ability to control the temporal characteristics of the gain-switched pulses mean this is a versatile source highly suited to a wide range of applications in the eye-safe region of the infrared, including spectroscopy, sensing and material processing, as well as being a practical seed source for pumping nonlinear processes. [Hide abstract]

09 10 11 12 13 14 2015 16

  1. 2D Saturable Absorbers for Fibre Lasers [Invited]

    R. I. Woodward, and E. J. R. Kelleher

    Applied Sciences, Vol. 5, 1440 (2015) or Download PDF [Show abstract]

    Two-dimensional (2D) nanomaterials are an emergent and promising platform for future photonic and optoelectronic applications. Here, we review recent progress demonstrating the application of 2D nanomaterials as versatile, wideband saturable absorbers for Q-switching and mode-locking fibre lasers. We focus specifically on the family of few-layer transition metal dichalcogenides, including MoS2, MoSe2 and WS2. [Hide abstract]

  2. Wideband saturable absorption in few-layer molybdenum diselenide (MoSe2) for Q-switching Yb-, Er- and Tm-doped fiber lasers

    R. I. Woodward, R. C. T. Howe, T. H. Runcorn, G. Hu, F. Torrisi, E. J. R. Kelleher, T. Hasan

    Optics Express, Vol. 23, 20051 (2015) or Download PDF [Show abstract]

    We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices. [Hide abstract]

  3. Duration-tunable picosecond source at 560 nm with watt-level average power

    T. H. Runcorn, R. T. Murray, E. J. R. Kelleher, S. V. Popov and J. R. Taylor

    Optics Letters, Vol. 40, 3085 (2015) or Download PDF [Show abstract]

    A pulse source at 560 nm that is tunable in duration between 50 ps–2.7 ns with > 1 W of average power and near diffraction-limited beam quality is demonstrated. The source is based on efficient (up to 50%) second-harmonic generation in a periodically-poled lithium tantalate crystal of a linearly-polarized fiber-integrated Raman amplifier operating at 1120 nm. A duration-tunable ytterbium master-oscillator power-fiber-amplifier is used to pulse-pump the Raman amplifier, which is seeded by a continuous wave distributed feedback laser diode at 1120 nm. The performance of the system using two different master oscillator schemes is compared. A pulse energy of up to 765 nJ is achieved with a conversion efficiency of 25% from the ytterbium fiber pump, demonstrating a compact and turn-key architecture for obtaining high peak-power radiation at 560 nm. [Hide abstract]

  4. Fiber-integrated frequency-doubling of a picosecond Raman laser to 560 nm

    T. H. Runcorn, T. Legg, R. T. Murray, E. J. R. Kelleher, S. V. Popov and J. R. Taylor

    Optics Express, Vol. 23, 15728 (2015) or Download PDF [Show abstract]

    We report the development of a fiber-integrated picosecond source at 560 nm by second harmonic generation of a Raman fiber laser. A picosecond ytterbium master oscillator power fiber amplifier is used to pulse-pump a Raman amplifier, which is seeded by a continuous wave distributed feedback laser diode operating at 1120 nm. The pulse train generated at 1120 nm is frequency-doubled in a fiber-coupled periodically-poled lithium niobate crystal module, producing 450 mW of average power at 560 nm with a pulse duration of 150 ps at a repetition rate of 47.5 MHz. The near diffraction-limited (M2 = 1.02) collimated output beam is ideal for super-resolution microscopy applications. [Hide abstract]

  5. Solution processes MoS2-PVA composite for sub-bandgap mode-locking of a wideband tunable ultrafast Er:fiber laser

    M. Zhang, R. C. T. Howe, R. I. Woodward, E. J. R. Kelleher, F. Torrisi, G. Hu, S. V. Popov, J. R. Taylor and T. Hasan

    Nano Research, Vol. 8, 1522 (2015) or Download PDF [Show abstract]

    We fabricate a free-standing few-layer molybdenum disulfide (MoS2)-polymer composite by liquid phase exfoliation of chemically pristine MoS2 crystals and use this to demonstrate a wideband tunable, ultrafast mode-locked fiber laser. Stable, picosecond pulses, tunable from 1535 nm to 1565 nm, are generated, corresponding to photon energies below the MoS2 material bandgap. These results contribute to the growing body of work studying the nonlinear optical properties of transition metal dichalcogenides that present new opportunities for ultrafast photonic applications. [Hide abstract]

  6. Few-layer MoS2 saturable absorbers for short-pulse laser technology: current status and future perspectives [Invited]

    R. I. Woodward, R. C. T. Howe, G. Hu, F. Torrisi, M. Zhang, T. Hasan and E. J. R. Kelleher

    Photonics Research, Vol. 3, A30 (2015) or Download PDF [Show abstract]

    Few-layer molybdenum disulfide (MoS2) is emerging as a promising quasi-two-dimensional material, further extending the library of suitable layered nanomaterials with exceptional optical properties for use in saturable absorber devices that enable short-pulse generation in laser systems. In this article, we catalog and review the nonlinear optical properties of few-layer MoS2, summarize recent progress in processing and integration into saturable absorber devices and comment on the current status and future perspectives of MoS2-based pulsed lasers. [Hide abstract]

  7. Fiber grating compression of giant-chirped nanosecond pulses from an ultra-long nanotube mode-locked fiber laser

    R. I. Woodward, E. J. R. Kelleher, S. Loranger, D. Popa, V. Wittwer, A. C. Ferrari, S. V. Popov, R. Kashyap and J. R. Taylor

    Optics Letters, Vol. 40, 387 (2015) or Download PDF [Show abstract]

    We demonstrate that the giant chirp of coherent, nanosecond pulses generated in an 846 m long, all-normal dispersion, nanotube mode-locked fiber laser can be compensated using a chirped fiber Bragg grating compressor. Linear compression to 11 ps is reported, corresponding to an extreme compression factor of ~100. Experimental results are supported by numerical modeling, which is also used to probe the limits of this technique. Our results unequivocally conclude that ultra-long cavity fiber lasers can support stable dissipative soliton attractors and highlight the design simplicity for pulse-energy scaling through cavity elongation. [Hide abstract]

09 10 11 12 13 2014 15 16

  1. Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoS2)

    R. I. Woodward, E. J. R. Kelleher, R. C. T. Howe, G. Hu, F. Torrisi, T. Hasan, S. V. Popov and J. R. Taylor

    Optics Express, Vol. 22, 31113 (2014) or Download PDF [Show abstract]

    We fabricate a few-layer molybdenum disulfide (MoS2) polymer composite saturable absorber by liquid-phase exfoliation, and use this to passively Q-switch an ytterbium-doped fiber laser, tunable from 1030 to 1070 nm. Self-starting Q-switching generates 2.88 μs pulses at 74 kHz repetition rate, with over 100 nJ pulse energy. We propose a mechanism, based on edge states within the bandgap, responsible for the wideband nonlinear optical absorption exhibited by our few-layer MoS2 sample, despite operating at photon energies lower than the material bandgap. [Hide abstract]

  2. Fiber-integrated 780 nm source for visible parametric generation

    D. J. J. Hu, R. T. Murray, T. Legg, T. H. Runcorn, M. Zhang, R. I. Woodward, J. L. Lim, Y. Wang, F. Luan, B. Gu, P. P. Shum, E. J. R. Kelleher, S. V. Popov, and J. R. Taylor

    Optics Express, Vol. 22, 29726 (2014) or Download PDF [Show abstract]

    We report the development of a fully fiber-integrated pulsed master oscillator power fibre amplifier (MOPFA) source at 780 nm, producing 3.5 W of average power with 410 ps pulses at a repetition rate of 50 MHz. The source consists of an intensity modulated 1560 nm laser diode amplified in an erbium fiber amplifier chain, followed by a fiber coupled periodically poled lithium niobate crystal module for frequency doubling. The source is then used for generating visible light through four-wave mixing in a length of highly nonlinear photonic crystal fiber: 105 mW at 668 nm and 95 mW at 662 nm are obtained, with pump to anti-Stokes conversion slope efficiencies exceeding 6% in both cases. [Hide abstract]

  3. Ultrafast fibre laser sources: Examples of recent developments [Invited review]

    M. Zhang, E. J. R. Kelleher, S. V. Popov and J. R. Taylor

    Optical Fiber Technology, Vol. 20, 666 (2014) or Download PDF [Show abstract]

    We summarise a number of recent experimental developments in the field of ultrafast compact all-fibre lasers, including: ionically-doped coloured glass saturable absorbers; Tm:fibre lasers utilising graphene around 2 μm; alternative layered materials including MoS2; passively synchronised, coupled-cavity ultrafast dual-wavelength fibre lasers; and schemes for the generation of high repetition rate femtosecond pulses based on phase modulation, and spectral masking of CW radiation. The breadth of light sources covered in this review highlights the diversity of approaches in ongoing research in the field of ultrafast fibre optics. [Hide abstract]

  4. Scalar Nanosecond Pulse Generation in a Nanotube Mode-Locked Environmentally Stable Fiber Laser

    R. I. Woodward, E. J. R. Kelleher, D. Popa, T. Hasan, F.Bonaccorso, A. C.Ferrari, S. V. Popov, J. R. Taylor

    Photon. Technol. Lett., Vol. 26, 1672 (2014) or Download PDF [Show abstract]

    We report an environmentally stable nanotube mode-locked fiber laser producing linearly-polarized, nanosecond pulses. A simple all-polarization-maintaining fiber ring cavity is used, including 300 m of highly nonlinear fiber to elongate the cavity and increase intracavity dispersion and nonlinearity. The laser generates scalar pulses with a duration of 1.23 ns at a center wavelength of 1042 nm, with 1.3 nm bandwidth and at 641 kHz repetition rate. Despite the long cavity, the output characteristics show no significant variation when the cavity is perturbed, and the degree of polarization remains at 97%. [Hide abstract]

  5. Double wall carbon nanotubes for wide-band, ultrafast pulse generation

    T. Hasan, Z. Sun, P. Tan, D. Popa, E. Flahaut, E. J. R. Kelleher, F. Bonaccorso, F. Wang, Z. Jiang, F. Torrisi, G. Privitera, V. Nicolosi and A. C. Ferrari

    ACS Nano, Vol. 8, 4836 (2014) or Download PDF [Show abstract]

    We demonstrate wideband ultrafast optical pulse generation at 1, 1.5 and 2 μm using a single polymer composite saturable absorber based on Double-Wall Carbon Nanotubes (DWNT). The freestanding optical quality polymer composite is prepared from nanotubes dispersed in water with polyvinyl alcohol as the host matrix. The composite is then integrated into Ytterbium- (Yb-), Erbium- (Er-) and Thulium- (Tm-) doped fiber laser cavities. Using this single DWNT-polymer composite, we achieve 4.85 ps, 532 fs and 1.6 ps mode-locked pulses at 1066, 1559 and 1883 nm, respectively, highlighting the potential of DWNTs for wideband ultrafast photonics. [Hide abstract]

  6. Stimulated Brillouin scattering of visible light in small-core photonic crystal fibers

    R. I. Woodward, E. J. R. Kelleher, S. V. Popov and J. R. Taylor

    Optics Letters, Vol. 39, 2330 (2014) or Download PDF [Show abstract]

    We characterize stimulated Brillouin scattering (SBS) of visible light in small-core photonic crystal fiber (PCF). Threshold powers under 532 nm excitation agree with established theory, in contrast to measured values up to five times greater than expected for Brillouin scattering of 1550 nm light. An isolated, single-peaked signal at a Stokes shift of 33.5 GHz is observed, distinct from the multi-peaked Stokes spectra expected when small-core PCF is pumped in the infrared. This wavelength-dependence of the Brillouin threshold, and the corresponding spectrum, are explained by the acousto-optic interactions in the fiber, governed by dimensionless length scales that relate the modal area to the core size, and the pump wavelength to PCF hole pitch. Our results suggest new opportunities for exploiting SBS of visible light in small-core PCFs. [Hide abstract]

  7. Chirped pulse formation in ultra-long mode-locked fiber lasers

    E. J. R. Kelleher and J. C. Travers

    Optics Letters, Vol. 39, 1398 (2014) or Download PDF [Show abstract]

    By modeling the giant chirped pulse formation in ultra-long, normally dispersive, mode-locked fiber lasers we verify convergence to a steady-state consisting of highly chirped and coherent, nanosecond-scale pulses, in good agreement with recent experimental results. Numerical investigation of the transient dynamics reveals the existence of dark soliton-like structures within the envelope of the initial noisy pulse structure. Quasi-stationary dark solitons can persist throughout a large part of the evolution from noise to a stable dissipative soliton solution of the mode-locked laser cavity. [Hide abstract]

09 10 11 12 2013 14 15 16

  1. Mid-infrared Raman-soliton continuum pumped by a nanotube-mode-locked sub-picosecond Tm-doped MOPFA

    M. Zhang, E. J. R. Kelleher, T. H. Runcorn, V. M. Mashinsky, O. I. Medvedkov, E. M. Dianov, D. Popa, S. Milana, T. Hasan, Z. Sun, F. Bonaccorso, Z. Jiang, E. Flahaut, B. H. Chapman, A. C. Ferrari, S. V. Popov and J. R. Taylor

    Optics Express, Vol. 21, 23261 (2013) or Download PDF [Show abstract]

    We demonstrate a mid-infrared Raman-soliton continuum extending from 1.9 to 3 μm in a highly germanium-doped silica-clad fiber, pumped by a nanotube mode-locked thulium-doped fiber system, delivering 12 kW sub-picosecond pulses at 1.95 μm. This simple and robust source of light covers a portion of the atmospheric transmission window. [Hide abstract]

  2. Widely tunable polarization maintaining photonic crystal fiber based parametric wavelength conversion

    R. T. Murray, E. J. R. Kelleher, S. V. Popov, A. Mussot, A. Kudlinski, and J. R. Taylor

    Optics Express, Vol. 21, 15826 (2013) or Download PDF [Show abstract]

    We report a near-visible parametric wavelength converter comprising a polarization-maintaining photonic crystal fiber (PM-PCF) pumped by a highly versatile diode-seeded master-oscillator power amplifier system based around 1.06 μm. The device is broadly tunable in wavelength (0.74–0.81 μm), pulse duration (0.2–1.5 ns) and repetition rate (1–30 MHz). A maximum anti-Stokes slope conversion efficiency of 14.9% is achieved with corresponding anti-Stokes average output powers of 845 mW, at a wavelength of 0.775 μm. [Hide abstract]

  3. Characterization of nonlinear saturation and mode-locking potential of ionically-doped colored glass filter for short-pulse fiber lasers

    M. Zhang, E. J. R. Kelleher, S. V. Popov and J. R. Taylor

    Optics Express, Vol. 21, 12562 (2013) or Download PDF [Show abstract]

    The nonlinear saturable absorption of an ionically-doped colored glass filter is measured directly using a Z-scan technique. For the first time, we demonstrate the potential of this material as a saturable asborber in fiber lasers. We achieve mode-locking of an ytterbium doped system. Mode-locking of cavities with all-positive and net-negative group velocity dispersion are demonstrated, achieving pulse durations of 60 ps and 4.1 ps, respectively. This inexpensive and optically robust material, with the potential for broadband operation, could surplant other saturable absorber devices in affordable mode-locked fiber lasers. [Hide abstract]

  4. Simultaneous scalar and cross-phase modulation instabilities in highly birefringent photonic crystal fiber

    A. Kudlinski, A. Bendahmane, D. Labat, S. Virally, R. T. Murray, E. J. R. Kelleher, A. Mussot

    Optics Express, Vol. 21, 8437 (2013) or Download PDF [Show abstract]

    We report the experimental observation of scalar and crossphase modulation instabilities by pumping a highly birefringent photonic crystal fiber in the normal dispersion regime at 45° to its principal polarization axes. Five sideband pairs (two scalar and three vector ones) are observed simultaneously in the spontaneous regime, four of which have a large frequency shift from the pump, in the range 79 – 93 THz. These results are in excellent agreement with phase-matching arguments and numerical simulations. [Hide abstract]

  5. CW-pumped short pulsed 1.12 μm Raman laser using carbon nanotubes

    C. E. S. Castellani, E. J. R. Kelleher, D. Popa, T. Hasan, Z. Sun, A. C. Ferrari, S. V. Popov and J. R. Taylor

    Laser Physics Letters, Vol. 10, 015101 (2013) or Download PDF [Show abstract]

    We demonstrate passive mode-locking of a Raman fiber laser at 1.12 μm, using a nanotube-based saturable absorber. A regular train of pulses, with a duration of 236 ps at the fundamental repetition frequency of the cavity, are generated by the all- normal dispersion oscillator. Importantly, this simple system is pumped with a continuous wave Yb fiber laser, removing the need for complex synchronous pumping schemes, where pulse- shaping depends on the action of the saturable absorber and a balance of dissipative processes. These results illustrate the flexibility of combining Raman amplification with a nanotube-based absorber for wavelength versatile pulsed sources. [Hide abstract]

09 10 11 2012 13 14 15 16

  1. Fission of solitons in continuous-wave supercontinuum

    E. J. R. Kelleher, M. Erkintalo and J. C. Travers

    Optics Letters, Vol. 37, 5217 (2012) or Download PDF [Show abstract]

    We use numerical simulations to revisit the generation of fiber supercontinua pumped by partially coherent continuous-wave (CW) sources. Specifically, we show that intensity fluctuations characteristic of temporal partial coherence can be described as a stochastic train of high-order solitons, whose individual dynamics drive continuum formation. For sources with sufficiently low coherence, these solitons actually undergo fission rather than modulation instability, changing the nature of the CW supercontinuum evolution. [Hide abstract]

  2. Tm-doped fiber laser mode-locked by graphene-polymer composite

    M. Zhang, E. J. R Kelleher, F. Torrisi, Z. Sun, T. Hasan, D. Popa, F. Wang, A. C. Ferrari, S.V. Popov, J. R. Taylor

    Optics Express, Vol. 20, 25077 (2012) or Download PDF [Show abstract]

    We demonstrate mode-locking of a thulium-doped fiber laser operating at 1.94 μm, using a graphene-polymer based saturable absorber. The laser outputs 3.6 ps pulses, with 0.4 nJ energy and an amplitude fluctuation 0.5%, at 6.46 MHz. This is a simple, low-cost, stable and convenient laser oscillator for applications where eye-safe and low-photon-energy light sources are required, such as sensing and biomedical diagnostics. [Hide abstract]

  3. Pump wave coherence, modulation instability and their effect on continuous-wave supercontinua [Invited review]

    E. J. R. Kelleher

    Optical Fiber Technology, Vol. 18, 268 (2012) or Download PDF [Show abstract]

    The effect of pump coherence on the evolution of continuous-wave (CW) supercontinua is explored within the framework of the generalised nonlinear Schrödinger equation. Recent results of experimental studies, using an amplified spontaneous emission (ASE) based CW pump source, with a selectable coherence time, confirm the trend observed numerically [1]: an optimum degree of partial pump coherence generates the broadest spanning continuum. The effect of third order dispersion on continuum expansion is discussed in the context of an optimum degree of pump coherence. Finally, a design guideline for CW pumped supercontinuum light sources is suggested, relating the optimum pump bandwidth to the modulation instability period. [Hide abstract]

  4. Synchronously pumped photonic crystal fiber-based optical parametric oscillator

    R. T. Murray, E. J. R. Kelleher, S. V. Popov, A. Mussot, A. Kudlinski, J. R. Taylor

    Optics Letters, Vol. 15, 3156 (2012) or Download PDF [Show abstract]

    We report the development of a compact, tunable synchronously pumped photonic crystal fiber (PCF)-based optical parametric oscillator (FOPO). The oscillator is pumped using a gain-switched laser diode producing 220 ps pulses around 1062 nm, amplified in a ytterbium doped amplifier to peak powers of 3.5 kW. The FOPO produces anti-Stokes pulses at wavelengths between 757 and 773 nm, with durations of 150 ps at average output powers exceeding 290 mW. The output slope efficiency of the device varies with output wavelength from 1.9 to 6.0%. [Hide abstract]

  5. Stable gain-guided soliton propagation in a polarized Yb-doped mode-locked fiber laser

    M. E. V. Pedersen, E. J. R. Kelleher, J. C. Travers, Z. Sun, T. Hasan, A. C. Ferrari, S. V. Popov, J. R. Taylor

    IEEE Photonics Journal, Vol. 4, 1058 (2012) or Download PDF [Show abstract]

    We demonstrate gain-guided dissipative soliton operation of a linearly polarized Yb- doped fiber laser, mode-locked by carbon nanotubes. In the regime of low nonlinear phase shift per cavity roundtrip, a dissipative soliton pulse can be supported by the finite gain bandwidth, without the need for strong spectral selection. The gain-guiding dynamics are confirmed by simulations. [Hide abstract]

  6. Role of pump coherence in the evolution of continuous-wave supercontinuum generation initiated by modulation instability

    E. J. R. Kelleher, J. C. Travers, S. V. Popov, J. R. Taylor

    Journal of the Optical Society of America B, Vol. 29, 502 (2012) or Download PDF [Show abstract]

    We report in detail, both experimentally and using numerical simulation, the efficiency of generation of supercontinua in optical fiber driven by modulation instability of a continuous-wave (CW) pump source. It is shown that the degree of pump coherence has a dramatic effect on the resulting spectral expansion and it is discussed how this can be explained by having the proper conditions for efficient modulation instability to break the CW pump light into a train of fundamental solitons that subsequently undergo self-Raman shift to longer wavelengths. It is proposed that an optimal pump bandwidth exists corresponding to the optimal degree of pump incoherence, defined as a function of the modulation instability period. [Hide abstract]

  7. Harmonic and single pulse operation of a Raman laser using graphene

    C. E. S. Castellani, E. J. R. Kelleher, Z. Luo, K. Wu, C. Ouyang, P. P. Shum, Z. Shen, S. V. Popov, J. R. Taylor

    Laser Physics Letters, Vol. 9, 223 (2012) or Download PDF [Show abstract]

    We present an all-fiber passively mode-locked Raman laser using graphene as a saturable absorber. Different lengths of a highly non-linear fiber presenting normal dispersion at both pump and signal wavelengths are used in the cavity to provide Raman amplification. The cavity is pumped by a continuous wave Raman laser at 1450 nm, and generates short pulses around 1550 nm, which depending on polarization and filtering parameters can be either at the repetition rate of the cavity or at higher harmonics of it. [Hide abstract]

09 10 2011 12 13 14 15 16

  1. Passive synchronization of all-fiber lasers through a common saturable absorber

    M. Zhang, E. J. R. Kelleher, A. S. Pozharov, E. D. Obraztsova, S. V. Popov, J. R. Taylor

    Optics Letters, Vol. 36, 3984 (2011) or Download PDF [Show abstract]

    We present the synchronization of two all-fiber mode-locked lasers, operating at 1.0 μm and 1.54 μm, coupled through the use of a shared single-wall carbon nanotube absorber. Both lasers operate in the soliton-regime, achieving a synchronized repetition rate of 13.08 MHz. The broadband absorption range of the single-wall carbon nanotubes allows the stable mode-locking behavior at 1 μm and 1.5 μm. The nonlinear coupling effects between two energy states of the carbon nanotube absorber result in stable synchronized pulses for hours of operation, with a large cavity mismatch of 1400 μm. [Hide abstract]

  2. Ultrafast Raman laser mode-locked by nanotubes

    C. E. S. Castellani, E. J. R. Kelleher, J. C. Travers, D. Popa, T. Hasan, Z. Sun, E. Flahaut, A. C. Ferrari, S. V. Popov, J. R. Taylor

    Optics Letters, Vol. 36, 3996 (2011) or Download PDF [Show abstract]

    We demonstrate passive mode-locking of a Raman fiber laser using a nanotube-based saturable absorber coupled to a net normal dispersion cavity. This generates highly chirped 500 ps pulses. These are then compressed down to 2 ps, with 1.4 kW peak power, making it a simple wavelength-versatile source for various applications. [Hide abstract]

  3. Picosecond bismuth-doped fiber MOPFA for frequency conversion

    B. H. Chapman, E. J. R. Kelleher, S. V. Popov, K. M. Golant, J. Puustinen, O. Okhotnikov and J. R. Taylor

    Optics Letters, Vol. 36, 3792 (2011) or Download PDF [Show abstract]

    We report the development of a bismuth-doped fiber master oscillator power fiber amplifier system. The system operates at 1177 nm, producing 28 ps pulses at 9.11 MHz repetition rate, with an output power of 150 mW and a peak pulse power of 580 W. We subsequently frequency double the output, resulting in a picosecond pulsed visible source operating at 588.5 nm, with a maximum average output power of 13.7 mW. [Hide abstract]

  4. Nanosecond pulse generation in lumped normally dispersive all-fiber mode-locked laser

    M. Zhang, E. J. R. Kelleher, E. D. Obraztsova, S. V. Popov, J. R. Taylor

    IEEE Photonics Technology Letters, Vol. 23, 1379 (2011) or Download PDF [Show abstract]

    We report an all-normal dispersion, all-fiber integrated ytterbium laser mode-locked by a single wall carbon nanotube (SWNT) saturable absorber, with a chirped fiber Bragg grating (CFBG) providing dispersion of 35.71 ps nm-1 allowing us to directly obtain nanosecond-scale duration pulses. In this large positive dispersion regime, mode-locking is initiated by the saturable action of the SWNT device, with pulse formation stabilized by the combined bandwidth limiting effect of the gain dispersion and the narrow reflection band of the CFBG. [Hide abstract]

  5. Amplification of picosecond pulses and gigahertz signals in bismuth-doped fiber amplifiers

    B. H. Chapman, E. J. R. Kelleher, K. M. Golant, S. V. Popov, J. R. Taylor

    Optics Letters, Vol. 36, 1446 (2011) or Download PDF [Show abstract]

    We demonstrate the capability for amplification of picosecond pulses in two bismuth-doped alumosilicate fibers. A spectrally filtered supercontinuum source is used to provide a train of picosecond pulses at discrete wavelengths within the gain bandwidth of bismuth fiber amplifiers. With a 30 m length of active fiber, a small signal gain at 1160 nm of over 20 dB is observed. In addition, we assess the viability of amplification of high repetition rate signals in such amplifiers, applying a 10 GHz modulation to a continuous wave Raman fiber laser operating at 1178 nm, finding that such signals are amplified without noticeable distortion. [Hide abstract]

  6. Vector solitons in a laser passively mode-locked by single-wall carbon nanotubes

    J. H. Wong, J. Wu, H. H. Liu, C. Ouyang, H. Wang, S. Aditya, P. Shum, S. Fu, E. J. R. Kelleher, A. Chernov, E. D. Obraztsova

    Optics Communications, Vol. 284, 2007 (2011) or Download PDF [Show abstract]

    Polarization Rotation Locked Vector Solitons (PRLVSs) are experimentally observed for the first time in a fiber ring laser passively mode-locked by a single-wall carbon nanotube (SWCNT) saturable absorber. Period-doubling of these solitons at certain birefringence values has also been observed. We show that fine adjustment to the intracavity birefringence can swing the PRLVSs from period-doubled to period-one state without simultaneous reduction in the pump strength. The timing jitter for both states has also been measured experimentally and discussed analytically using the theoretical framework provided by the Haus model. [Hide abstract]

  7. Using the E22 transition of carbon nanotubes for fiber laser mode-locking

    J. C. Travers, J. Morgenweg, E. D. Obraztsova, A. I. Chernov, E. J. R. Kelleher and S. V. Popov

    Laser Physics Letters, Vol. 8, 144 (2011) or Download PDF [Show abstract]

    We characterize the saturable absorption of the second (E22) electronic transition of a sample of single-walled carbon nanotubes and use it to mode-lock an ytterbium fiber ring laser. The modulation depth of ~15% was found to be similar to the corresponding E11 transition (~13%), but the saturation intensity (~220 MW cm-2) about an order of magnitude larger (~10 MW cm-2). We achieved a 15 MHz mode-locked pulse train with an output pulse duration of 6.5 ps. For comparison we also demonstrate stable mode-locking on the E11 transition, of the same nanotubes, with an erbium fiber ring laser, producing 1.1 ps pulses. Using the E22 transition should enable the use of carbon nanotube saturable absorbers at shorter wavelengths than currently possible with the E11 transition, which are limited by the smallest achievable nanotube dimensions. [Hide abstract]

09 2010 11 12 13 14 15 16

  1. Bismuth fiber integrated laser mode-locked by carbon nanotubes

    E. J. R. Kelleher, J. C. Travers, Z. Sun, A. C. Ferrari, K. M. Golant, S. V. Popov and J. R. Taylor

    Laser Physics Letters, Vol. 7, 790 (2010) or Download PDF [Show abstract]

    We demonstrate passive mode-locking of a Bi-doped fiber laser using a nanotube-based saturable absorber. We achieve stable mode-locking in both the all-normal and net anomalous dispersion regimes. Near transform-limited 4.7 ps soliton pulses are generated in the average-soliton regime, with a chirped fiber Bragg grating used for dispersion compensation to retain an all-fiber format. [Hide abstract]

  2. A stable, wideband tunable, near transform-limited, graphene-mode-locked, ultrafast laser

    Zhipei Sun, Daniel Popa, Tawfique Hasan, Felice Torrisi, Fengqiu Wang, Edmund J. R. Kelleher, John C. Travers, Valeria Nicolosi, Andrea C. Ferrari

    Nano Research, Vol. 3, 653 (2010) or Download PDF [Show abstract]

    We report an ultrafast laser mode-locked with a graphene saturable absorber. The linear dispersions of the Dirac electrons in graphene enable wideband tunability. We get ∼1 ps pulses, tunable between 1525 and 1559 nm, with stable mode-locking, insensitive to environmental perturbations. [Hide abstract]

  3. Nonlinear coupling of relative intensity noise from pump to a fiber ring laser mode-locked with carbon nanotubes

    K. Wu, J. H. Wong, P. P. Shum, S. Fu, C. Ouyang, H. Wang, E. J. R. Kelleher, A. I. Chernov, E. D. Obraztsova, J. Chen

    Optics Express, Vol. 18, 16663 (2010) or Download PDF [Show abstract]

    Pump relative intensity noise (RIN) has been recognized as a major source of noise in mode-locked lasers. The coupling of RIN from the pump to the output of a passively mode-locked fiber laser (PMFL) is systematically investigated using a pump modulation technique. It is found that the linear RIN coupling ratio from pump to PMFL is decreased with an increase in modulation frequency and is independent of modulation power. Moreover, the nonlinear RIN coupling from pump to PMFL is clearly demonstrated with a square wave modulated pump. The nonlinear RIN coupling ratio is noise power dependent. An exponential decay model based on the view of gain modulation is proposed and explains well the behavior of the nonlinear coupling phenomena. [Hide abstract]

  4. Observation of timing jitter reduction induced by spectral filtering in a fiber laser mode locked with a carbon nanotube-based saturable absorber

    C. Ouyang, P. P. Shum, H. Wang, J. H. Wong, K. Wu, S. Fu, R. Li, E. J. R. Kelleher, A. I. Chernov, E. D. Obraztsova

    Optics Letters, Vol. 35, 2320 (2010) or Download PDF [Show abstract]

    A self-starting passively mode-locked fiber laser with a carbon nanotube-based saturable absorber and a fiber-based bandpass filter (BPF) is proposed. Incorporation of a BPF into the cavity leads to a great reduction of its timing jitter from 84.8 to 29.1 fs (10 Hz - 3 MHz ). This happens because the filtering effect can weaken the fluctuation of the central wavelength induced by the quantum noise, being one of the important contributions to timing jitter in the optical amplifying process. [Hide abstract]

  5. Narrow Linewidth Bismuth-Doped All-Fiber Ring Laser

    E. J. R. Kelleher, J. C. Travers, K. M. Golant, S. V. Popov, J. R. Taylor

    IEEE Photonics Technology Letters, Vol. 22, 793 (2010) or Download PDF [Show abstract]

    We report a novel narrow linewidth Bismuth-doped all-fiber ring laser, operating at 1177 nm. We achieve a 10-mW output in a 4 GHz linewidth, direct from the oscillator under 7 W of pumping, delivered by an Yb-fiber laser. Mode suppression in the 50 m unidirectional ring cavity is provided by a narrowband fiber Bragg grating and two fiber integrated Fabry-Perot (FP) filters. The FP filters provide a factor of 20 mode suppression, while improving the relative intensity noise by up to 20 dB/Hz. The optical signal-to-noise ratio (OSNR) is ~60 dB. [Hide abstract]

2009 10 11 12 13 14 15 16

  1. Generation and direct measurement of giant chirp in a passively mode-locked laser

    E. J. R. Kelleher, J. C. Travers, E. P. Ippen, Z. Sun, A. C. Ferrari, S. V. Popov and J. R. Taylor

    Optics Letters, Vol. 34, 3526 (2009) or Download PDF [Show abstract]

    We evaluate the shape and chirp of nanosecond pulses from a fiber laser passively mode locked with a nanotube-based saturable absorber by using a synchronously scanning streak camera and a monochromator to directly measure the pulse spectrogram. We show that the stable sech2 output pulse possesses a predominantly linear chirp, with a residual quartic phase and low noise. Comparison with analytical mode-locking theory shows a good quantitative agreement with the master equation mode-locking model. [Hide abstract]

  2. Nanosecond-pulse fiber lasers mode-locked with nanotubes

    E. J. R. Kelleher, J. C. Travers, Z. Sun, A. G. Rozhin, A. C. Ferrari, S. V. Popov and J. R. Taylor

    Applied Physics Letters, Vol. 95, 111108 (2009) or Download PDF [Show abstract]

    We demonstrate that mode-locking of ytterbium fiber lasers with a carbon nanotube saturable absorber can produce pulses ranging from 20 ps to 2 ns at repetition rates between 21 MHz and 177 kHz, respectively, depending on cavity length. Nonlinear polarization evolution is not responsible for mode-locking. Even in the nanosecond regime, clean single pulses are observed and the pulse train exhibits low jitter. Combined with extremely large chirp, these properties are suited for chirped-pulse amplification systems. [Hide abstract]

Conference papers

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